Industries like aeronautic industry, shipbuilding industry and train manufacturing industry are dealing with large workpieces. In such industries, and also in manufacturing industry in general, it is common to carry out manufacturing operations as measuring, drilling, milling, cutting, inspecting, fixing.
End-effectors for such operations are well known in the art and form no part of the present invention; however the term “end-effector” as used hereinafter should be understood to embrace all such apparatus for performing any such operation.
The term “manipulation” as used hereinafter should be understood to embrace all such operations for holding, positioning end-effectors to required positions with required orientations.
To automate those operations for large workpiece, systems are required to be able to have following properties:                Good rigidity and accuracy at any operation location        Large workspace        Reconfigurable workspace        
Flight simulators such as the Stewart platform [Stewart D., “A platform with six degrees of freedom,” in Proc. Institute of Mechanical Engr., pp. 371-386, vol. 180, 1965] have been used and studied as parallel manipulators. Based on parallel mechanisms, various manipulators with 6 degrees of freedom (DOFs), 5 DOFs, 4 DOFs, 3 DOFs and 2 DOFs are proposed.
These families of manipulators can be described as two platforms (a mobile plate and a fixed plate) connected by several kinematic chains which hereinafter will be referred to as legs of parallel manipulators. With certain joints within these legs being actuated, the mobile plate can be moved with certain degrees of freedom with respect to the fixed plate. They are proposed in order to build manipulators with good rigidity and/or good accuracy.
However, most of the parallel manipulators have limited workspace. Once the dimensions of the components of parallel manipulators are determined, the movement of the mobile plate regarding the fixed plate is limited to its predefined workspace. In prior art, the following solutions have been proposed to overcome such drawbacks:                Parallel manipulators made reconfigurable in order to form machines with different workspaces [Xi, Fengeng, Xu, Yuonan, Xiong, Guolian. “Design and analysis of a re-configurable parallel robot”, Mechanisms and Machine Theory, pp. 191-211, vol 41, l2, 2006].        Parallel manipulators made transportable, for example, as those disclosed in the U.S. Pat. No. 5,987,726. They can be installed on different locations such as floors, fixtures etc.        For obtaining larger workspaces, parallel manipulators are installed on various mobile platforms such as: the guide based system [Pekka Pessi, “Novel robot solutions for carrying out field joint welding and machining in the assembly of the vacuum vessel of ITER”, Ph.D. Thesis, Lappeenranta University of technology, Finland 2009].        
The reconfiguration of reconfigurable parallel manipulators in prior art requires a lot of machine down time. Changing the work location of the transportable parallel manipulators is also a very time-consuming process. Putting parallel manipulators on another mobile device such as wheeled, tracked and legged systems, represents additional components and controls of the locomotion system. Building guides with high stiffness and accuracy in a long distance represents tedious civil works and very high costs.
One of the specificities of parallel robots (and some serial robots that include closed kinematic chains) is the presence of passive joints in addition to a plurality of legs which connect a mobile plate to a fixed plate. Because the plurality legs forms the closed kinematic chains which impose kinematic constrains to the systems, there is no need to actuate every joint of such robots. The presence of the pivotal joints helps to build robots with relatively higher efficiency regarding to robots with all joints actuated. As a plurality of legs may enforce the rigidity as well as other properties of a robot, parallel robots attract more and more intentions for manufacturing applications.
However, with a plurality of legs connecting the mobile plate and the fixed plate, the volume of the robot's workspace is penalized severely. To enlarge workspace, conventional parallel manipulators are mounted on another mobile platform such as wheeled robots, tracked robots and legged robots. This involves extra actuators and control means of the mobile platform to the systems. When long guides are built to enlarge the workspace of parallel manipulators, high rigidity of the guides is required in order to minimize the vibrations and deflections and to increase the positioning accuracy. This leads to tedious civil works and less flexibility for production.